The present invention relates generally to monitors for gauges and more specifically to a nonelectrical monitor and alarm for use in hazardous environments.
The use of mechanical indicators such as gauges and another annunciators is well known. With the advent of relatively inexpensive integrated circuits, electrical gauges and alarms have replaced the mechanical gauges and indicators. In certain environments, the possibility of any sort of electrical spark is very hazardous. An example of one such environment is in the plastic and coating spraying industry where resin and catalysts are mixed together and sprayed onto a surface. There are many variables which must be monitored in the spraying environment. The spraying environment generally includes a series of mechanical gauges, operating on pressure, to indicate the pressures throughout the system as well as flow rates. The use of microprocessors and other forms of electrical equipment are used to interpret these electric signals to determine the flow and mass rate as well as the total amount of material being dispensed. Not only are these electrical systems somewhat expensive, but again they cannot be used in hazardous environments where any sort of electrical spark is considered dangerous. Also, electrical systems must met strict Underwriters and local codes and regulations.
One of the problem areas for which an alarm or monitor is very important is the flow rate of the catalyst. If the flow rate fluctuates, the resulting mixture will be over or under catalized and therefore produce a defective product or coating. Large variations in the flow rate would become obvious to the operator, but not in sufficient time to prevent forming an undesirable portion or layer and thus necessitate scrapping the whole product. Similarly small variations would not be obvious to the operator and could create areas or layers of undesirable composition which would fail in use.
Also, in internal mix guns where the catalyst is mixed with the resin, the mixture will set if the spraying operation is stopped for a period exceeding the set up time of the material. Normally at the termination of a job, the operator flushes the gun with a solvent. In some situations, the operator interrupts the spraying before finishing the job for a period longer than the set up time. This plugs the gun and cannot be remedied by flushing.
Thus, it is an object of the present invention to provide a nonelectrical alarm system for gauges which indicates when the signal being monitored by the gauge is out of an acceptable range.
Another object of the present invention is to provide a nonelectrical alarm system having a sensor which is capable of being used with any gauge and adjustable as to the value and range of the value to be monitored by the sensor.
A still even further object of the present invention is to provide an alarm or monitoring system for indicating to the operator to flush the system.
These and other objects of the invention are achieved by positioning a nonelectrical sensor to sense the position of a needle of a gauge as it moves along a path and providing the sensed nonelectrical signal to a nonelectrical annunciator for annunciating when the needle is not at a predetermined position. The sensor is adjustably mounted with respect to the path of the needle. This is achieved by mounting the sensor to a transparent face plate of the gauge, unsecuring the face plate and adjusting the face plate to position the sensor at the desired position on the gauge and then resecuring the face plate. If the path of the needle is a portion of a circle, and the face plate and the recess, in which it is mounted, are circular, their centers are all coaxial.
A range portion is provided on a standard needle and the sensor is positioned to sense the position of the range portion. The range portion has a length along the path which defines the range or sensitivity of the alarm. The range portion of the needle may be adjusted in itself or may be replaced with various length range portions. The gauge, the sensor and the annunciator are preferably pneumatic.
Although this system will be described for plastic and coating spraying systems, it may be used with any gauge having a needle, in a hazardous or non-hazardous environment, and for any material dispensing system.
A nonelectrical flush alarm or monitor may also be provided. The flush alarm includes a sensor to sense that the pump of a spraying or dispensing system is operating. If this sensor does not provide a signal to a timer for a preset period, the timer will produce a timed out signal which will be annunciated by an annunciator. The preset period of the timer is the set time of the plastic material. The sensor senses the mechanical movement of the pump which is actuated during spraying or dispensing. The sensor, timer and annunciator are preferably pneumatic.
The flush alarm and the gauge monitoring alarm may be provided in a single housing with separate and distinct annunciators as well as a common annunciator. The common annunciator may be an audible annunciator warning the operator that there is a problem. Then the operator consults one of the individual annunciators, which preferably are visual annunciators, indicating the problem to be addressed. This may be either that the gauge is reading a value outside the desired range or that the spraying or dispensing process has been interrupted for a period which exceeds the set time of the material. The flush alarm is most desirable with internal mix guns wherein the catalyst and resin are mixed internal to the gun and therefore will set in the gun if not flushed.